Prophylactic Oral Vancomycin May Prevent C Difficile Infections, Raise Risk of Gram-Negative Bacteremia in Stem Cell Transplant Recipients

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Preventive use of the oral antibiotic vancomycin may be effective at reducing the risk of Clostridioides difficile infections but may increase the risk of gram-negative bacteremia in stem cell transplant recipients, according to new findings presented by Vartanov et al at the 2024 Tandem Meetings: Transplantation & Cellular Therapy Meetings of the American Society for Transplantation and Cellular Therapy and the Center for International Blood & Marrow Transplant Research (Abstract 616).


Patients who undergo stem cell transplants as part of their treatment for hematologic malignancies such as lymphoma, leukemia, multiple myeloma, and myelodysplastic syndromes may be at a higher risk of life-threatening infections than the general population.

In particular, C difficile infections—an overgrowth of bacteria in the gastrointestinal tract—are a significant source of increased morbidity and mortality among these patients. Prior research has demonstrated that taking vancomycin as a preventive measure can lessen the risk of C difficile infections, but sufficient data are not yet available to make it a guideline-directed therapy.

In most cases, gram-negative bacteremia is treatable and curable, but it can also be the cause of sepsis, septic shock, and even death for patients undergoing stem cell transplants.

Study Methods and Results

In the new retrospective study, researchers conducted an extended follow-up analysis to evaluate the safety and efficacy of oral vancomycin as prophylaxis in 441 patients who received hematopoietic stem cell transplants between March 2021 and May 2023. The patients were divided into an experimental group who received the oral vancomycin and a control group who didn’t receive the treatment.

The researchers confirmed that receiving oral vancomycin prophylactically did reduce the rate of C difficile infections in stem cell transplant recipients. Compared with the control group, they found that the experimental group had a lower rate of infections (7% vs 13%). However, the researchers also observed that the rate of gram-negative bacteremia was higher in the experimental group (21.8% vs 13%).


The researchers emphasized the importance of screening all patients undergoing stem cell transplants and only administering prophylactic vancomycin in those who screen positive or have a history of C difficile infections.

“As we reported a year prior, this extended analysis shows that yes, vancomycin does reduce the C difficile infection rate,” highlighted lead study author Alexander Vartanov, MD, a third-year fellow in the Department of Hematology/Oncology at Fox Chase Cancer Center. “[W]hat was interesting is that one of our secondary outcomes, specifically bacterial infections in the blood with gram-negative bacteria, was higher for the patients who received the vancomycin prophylaxis. So even though generally that group was somewhat protected from C difficile infections, they were at higher risk of developing gram-negative bacteremia. That posed a little bit of a cautionary tale for us. It’s exciting to learn from our quality improvement projects and see how we can benefit patients,” he concluded.

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